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Temporally coherent supercontinuum sources constitute an attractive alternative to bulk crystal-based sources of few-cycle light pulses. We present a monolithic fiber-optic configuration for generating transform-limited temporally coherent supercontinuum pulses with central wavelength at 1.06 µm and duration as short as 13.0 fs (3.7 optical cycles). The supercontinuum is generated by the action of self-phase modulation and optical wave breaking when pumping an all-normal dispersion photonic crystal fiber with pulses of hundreds of fs duration produced by all-fiber chirped pulsed amplification. Avoidance of free-space propagation between stages confers unequalled robustness, efficiency and cost-effectiveness to this novel configuration. Collectively, the features of all-fiber few-cycle pulsed sources make them powerful tools for applications benefitting from the ultrabroadband spectra and ultrashort pulse durations. Here we exploit these features and the deep penetration of light in biological tissues at the spectral region of 1 µm, to demonstrate their successful performance in ultrabroadband multispectral and multimodal nonlinear microscopy.

We report on the conception, fabrication and characterization of a new concept of optical fiber enabling a precise control of the ratio between the 2 nd and 4 th -order of chromatic dispersion (respectively β 2 and β 4 ) at 1.55 µm which is at the heart of the Four-Wave-Mixing (FWM) generation. For conventional highly nonlinear fiber the sensitivity of this ratio to fiber geometry fluctuations is very critical, making the fabrication process challenging. The new design fiber reconciles the accurate control of chromatic dispersion properties and fabrication by standard stack and draw method, allowing a robust and reliable method against detrimental fluctuations parameters during the fabrication process. Experimental frequency conversion with FWM in the new design fiber is demonstrated.

We present a detailed study on the generation of widely tunable visible light through four wave mixing in specifically designed micro-structured fibers. The fiber's properties are optimized for an efficient conversion to the visible and near infrared with a combined tunability from 620 to 910 nm of a picosecond Yb-doped tunable source for biomedical applications.

Very large mode area, active optical fibers with a low high order mode content in the actively doped core region were designed by removing the inner cladding symmetry. The relevance of the numerical approach is demonstrated here by the investigation of a standard air-silica Large Pitch Fiber, used as a reference. A detailed study of all-solid structures is also performed. Finally, we propose new kinds of geometry for 50 μm core, all-solid microstructured fibers enabling a robust singlemode laser emission from 400 nm to 2200 nm.

We report about a new type of nonlinear photonic crystal fibers allowing broadband four-wave mixing and supercontinuum generation. The microstructured optical fiber has a structured core consisting of a rod of highly nonlinear glass material inserted in a silica tube. This particular structure enables four wave mixing processes with very large frequency detuning (>135 THz), which permitted the generation of a wide supercontinuum spectrum extending over 1650 nm after 2.15 m of propagation length. The comparison with results obtained from germanium-doped holey fibers confirms the important role of the rod material properties regarding nonlinear process and dispersion.